docs: def replace_body_vars(self, body):
          """Given a multiline string that is the body of the job script, replace
          the placeholders for environment variables with backend-specific
          realizations, and return the modified body. See the `job_vars`
          attribute for the mappings that are performed.
          """
          for key, val in self.job_vars.items():
              body = body.replace(key, val)
          return body